Overground robotic training effects on walking and secondary health conditions in individuals with spinal cord injury: systematic review

Abstract

Overground powered lower limb exoskeletons (EXOs) have proven to be valid devices in gait rehabilitation in individuals with spinal cord injury (SCI). Although several articles have reported the effects of EXOs in these individuals, the few reviews available focused on specific domains, mainly walking. The aim of this systematic review is to provide a general overview of the effects of commercial EXOs (i.e. not EXOs used in military and industry applications) for medical purposes in individuals with SCI. This systematic review was conducted following the PRISMA guidelines and it referred to MED-LINE, EMBASE, SCOPUS, Web of Science and Cochrane library databases. The studies included were Randomized Clinical Trials (RCTs) and non-RCT based on EXOs intervention on individuals with SCI. Out of 1296 studies screened, 41 met inclusion criteria. Among all the EXO studies, the Ekso device was the most discussed, followed by ReWalk, Indego, HAL and Rex devices. Since 14 different domains were considered, the outcome measures were heterogeneous. The most investigated domain was walking, followed by cardiorespiratory/metabolic responses, spasticity, balance, quality of life, human-robot interaction, robot data, bowel functionality, strength, daily living activity, neurophysiology, sensory function, bladder functionality and body composition/bone density domains. There were no reports of negative effects due to EXOs trainings and most of the significant positive effects were noted in the walking domain for Ekso, ReWalk, HAL and Indego devices. Ekso studies reported significant effects due to training in almost all domains, while this was not the case with the Rex device. Not a single study carried out on sensory functions or bladder functionality reached significance for any EXO. It is not possible to draw general conclusions about the effects of EXOs usage due to the lack of high-quality studies as addressed by the Downs and Black tool, the heterogeneity of the outcome measures, of the protocols and of the SCI epidemiological/neurological features. However, the strengths and weaknesses of EXOs are starting to be defined, even considering the different types of adverse events that EXO training brought about. EXO training showed to bring significant improvements over time, but whether its effectiveness is greater or less than conventional therapy or other treatments is still mostly unknown. High-quality RCTs are necessary to better define the pros and cons of the EXOs available today. Studies of this kind could help clinicians to better choose the appropriate training for individuals with SCI.

Keywords: Exoskeleton; Outcome measures; Rehabilitation; Robotic; Spinal cord injury.

Fig. 1

PRISMA flow diagram of the study selection process

Fig. 2

Number of individuals with SCI enrolled according to the lesion level (cervical, thoracic or lumbar SCI) across the 41 included studies. Ekso device: green columns; ReWalk device: blue columns; Indego device: red columns; HAL device: black columns; Rex device: orange columns. Individuals are grouped into AIS A plus AIS B group (left frame) and AIS C plus AIS D group (right frame)

Fig. 3

Percentage distributions of number of participants, minimum number of sessions per week and total number of sessions across the 41 included studies

Fig. 4

Number of the studies included in the review for each EXO (a) and number of studies addressing each domain (b). Ekso device: green columns; ReWalk device: blue columns; Indego device: red columns; HAL device: black columns; Rex device: orange columns. [Card./Met.: Cardiorespiratory and Metabolic responses; QoL: Quality of Life; HRI: Human Robot Interaction; Bowel_f: Bowel functionality; ADL: Activities of Daily Living; Neuroph.: Neurophysiology; Sensory_f: Sensory function; Bladder_f: Bladder functionality; Body/Bone: Body composition and bone density]

Fig. 5

Total numbers of studies addressing the different domains for each EXO according to TSI (subacute, chronic, subacute plus chronic SCI and unspecified TSI). For each domain and for each EXO lighter tone columns represent the number of studies with no significant data reported by Authors, while darker tone columns represent the number of studies for which significant results were pointed out by Authors [Card./Met.: Cardiorespiratory and Metabolic responses; QoL: Quality of Life; HRI: Human Robot Interaction; Bowel_f: Bowel functionality; ADL: Activities of Daily Living; Neuroph.: Neurophysiology; Sensory_f: Sensory function; Bladder_f: Bladder functionality; Body/Bone: Body composition and bone density]

Fig. 6

Percentage of studies including at least one outcome measures for each domain with significant improvements after EXOs training (a). Same data are reported in detail for Ekso, ReWalk, Indego and HAL devices (b)